摘要
矩阵A的特征值的集合(含重数)记为σ(A),A的惯量是指三元有序数组i(A)=(i+(A),i-(A),i0(A)),其中i+(A),i-(A)和i0(A)分别表示具有正,负,零实部特征值的个数.n阶符号模式矩阵S=(sij)是指元素取自{1,-1,0}或者{+,-,0}的矩阵,S的定性矩阵类是指集合Q(S)={A=(aij)∈Mn(R):对所有的i和j,sign(aij)=sij}.S的惯量是指集合i(S)={i(A):A∈Q(S)}.若对任意满足n1+n2+n3=n的非负三元数组(n1,n2,n3),都有(n1,n2,n3)∈i(S),则称符号模式S为惯量任意模式.考虑n阶符号模式Kn=(kij)n×n:当1≤j-i≤n-2或i=j=n时,kij=1;当1≤i-j≤n-2或i=j=1时,kij=-1;当|i-j|=n-1时,kij可以取任意固定值;其余情形时,kij=0.本文证明了Kn(n≥3)是惯量任意模式.
The set of all eigenvalues (counting multiplicities) of a matrix A is denoted by σ(A) ,and the inertia of A is the ordered triple i(A)=(i+ (A),i_(A),io(A)),in which i+ (A),i_(A) and io(A) are the numbers of eigenvalues with positive, negative and zero real parts, respectively. An n × n sign pattern S=(sij ) has sij∈ { 1,-1,0} or sij ∈ { +,-, 0 }, and the qualitative class of S is Q(S) = {A= (aij)∈ M. (R) : sign(aij ) = sij for all i,j}. The inertia of S is the set of ordered triplesi(S)={i(A):A∈Q(S)}. An n×n sign pattern S is an inertially arbitrary pattern (IAP) if (n1,n2,n3)∈ i(S) for each nonnegative triple (n1 ,n2, n3 ) with n1 + n2 + n3 = n. Consider the n × n sign pattern Kn, where K. is the pattern with positive entry (i,j) for 1≤ j-i≤n-2 or i=j=n,negative entry (i,j) for 1≤ i-j≤n-2 or i=j=1,arbitrary entry (i,j) for |i-j| =n-1 and zero entry otherwise. In this paper,it is proved that K, is an IAP for n≥3.
出处
《徐州师范大学学报(自然科学版)》
CAS
2006年第3期7-10,46,共5页
Journal of Xuzhou Normal University(Natural Science Edition)
基金
Research supported by the National Natural Science Foundation of China(10471037)
关键词
符号模式
惯量
惯量任意
蕴含稳定
sign patterns inertia
inertially arbitrary
potentially stable